GB2329642A - Low density, low water all MDI flexible foams - Google Patents

Abstract

Resin compositions useful for production of polyurethane foams comprise (a) an isocyanate-reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500, (b) a catalyst, (c) a blowing agent consisting of water, (d) a crosslinker and (e) optionally a surface active agent. The compositions can be reacted with isocyanate compositions to provide low-density, flexible polyurethane foams having an average density of less than about 3.5 pcf.

Description

LOW DENSITY, LOW WATER ALL MDI FLEXIBLE FOAMS Desription The present invention relates to polyurethane compositions and more particularly to polyurethane compositions employing diphenylmethane diisocyanates and polyols including a relatively high ethylene oxide content to form relatively soft diphenylmethane isocyanate foams.

Compositions employing a reaction mixture of polyisocyanates with polyols in the presence of catalysts and blowing agents to manufacture polyurethane foams have been known for years. The polyisocyanates most commonly employed are generally either toluene diisocyanates (TDI's), diphenylmethane diisocyanates (MDI's), or polymethylene polyphenylene polyisocyanates (polymeric MDI's) depending largely upon the desired end product properties for the resulting forms. For example, at a given water level, TDI formulations tend to result in lower density foams than MDI formations. However, TDI is generally more expensive than MDI which is reflected in the cost of the end products. Further, MDI or polymeric MDI based foams are often preferable in terms of ease of manufacture, magnitude of load bearing latitude, and diversity of product grade, among others.

The polyol composition employed in association with a given isocyanate also contributes greatly to the properties of the foamed end product. For example, certain polyols such as those containing high ethylene oxide/propylene oxide ratio heterics are known to cause cell opening which is often desirable. However, such polyols lead to higher density foams which is often undesirable.

Thus, there is a need in the art for polyurethane foam compositions which employ MDI and/or poloymeric MDI but give rise to foams having relatively low densities as are achieved utilizing TDI.

In view of the apparent need in the art for low density foams producible using relatively low water levels and MDI or polymeric MDI compositions, according to one aspect, the present invention relates to a polyurethane foam comprising the reaction mixture of: a) an isocyanate reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500; b) a catalyst; c) a blowing agent consisting of water; d) a crosslinker; e) optionally a surface active agent; and f) an isocyanate composition wherein the resulting foam has an average density of less than about 3.5 pcf.

According to a second aspect, the present invention relates to a resin useful for the production of polyurethane foams comprising: a) an isocyanate reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500; b) a catalyst; c) a blowing agent consisting essentially of water; d) a crosslinker; and e) optionally a surface active agent.

Surprisingly, it was discovered that polyurethane foams produced by reacting an MDI composition with a blended polyol including both ethylene oxide and propylene oxide heterics and at least one ethylene oxide capped polyol gave rise to foams having a relatively low density, i.e. below about 2.8 pcf. Generally, an ethylene oxide heteric polyol added to a resin composition will result in polyurethane foams having a higher density than those foams which employ polyols having little or no ethylene oxide heteric polyol.

The foams provided in accordance with the teachings of the present invention are low density, low water, MDI flexible urethane foams. The foams are polyisocyanate based meaning that they are made by reacting the reactive ingredients in a polyol composition with an organic isocyanate.

The polyol composition comprises a blended polyol including at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol, water as a blowing agent, a polyurethane linkage promoting catalyst, a surfactant, and optionally fillers, flame retardants, stabilizers, fungicides, and bacteriostats.

Turning to the ingredients of the polyol composition, there is provided a polyol blend including at least one ethylene oxide/ propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has a weight average molecular weight of greater than 4200 and, more preferably, between about 4700 to about 6800. The polyol blend has an average hydroxyl number ranging from 20 to 60 mgKOH/g and an average functionality of at least 2.0. In a preferred embodiment, the polyol blend will have an average hydroxyl number ranging from about 25 to about 45 mgKOH/g and an average functionality of at least 3.0.

Preferably, the amount of ethylene oxide/propylene oxide heteric polyol employed in the blend will be between about 8.0 wt. % to about 30.0 wt. %, more preferably 10.0 wt. % to about 20.0 % and still more preferably, between about 12.0 wt. % to about 16.0 wt.

%. The amount of ethylene oxide capped polyol employed in the polyol blend will preferably be between about 18.0 wt. % to about 24.0 wt. % and still more preferably, between about 20.0 wt. % to about 22..0 wt. t. Thus, the total amount of the ethylene oxide/ propylene oxide heteric polyol and the ethylene oxide capped polyol will be at least 26.0 wt. % based on the total amount of the polyol blend.

Examples of useful polyols which may be employed in addition to the above described polyols include polythioether polyols, polyester amides and polyacetals containing hydroxyl groups, aliphatic polycarbonates containing hydroxyl groups, amine terminated polyoxyalkylene polyethers, and preferably, polyester polyols, polyoxyalkylene polyether polyols, and graft dispersion polyols.

The term "polyester polyol" as used in this specification and claims includes any minor amounts of unreacted polyol remaining after the preparation of the polyester polyol and/or unesterified polyol (e.g., glycol) added after the preparation of the polyester polyol. The polyester polyol can include up to about 40 weight percent free glycol.

Suitable polyester polyols can be produced, for example, from organic dicarboxylic acids with 2 to 12 carbons, preferably aliphatic dicarboxylic acids with 4 to 6 carbons, and multivalent alcohols, preferably diols, with 2 to 12 carbons, preferably 2 to 6 carbons. Examples of dicarboxylic acids include suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used individually or in mixtures, Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives may also be used such as dicarboxylic acid mono- or di- esters of alcohols with 1 to 4 carbons, or dicarboxylic acid anhydrides. Dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid in quantity ratios of 20 - 35: - 35 - 50:20 - 32 parts by weight are preferred, especially adipic acid. Examples of divalent and multivalent alcohols, especially diols, include ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1, 10-decanediol, glycerine and trimethylolpropanes, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, tetramethylene glycol, 1,4-cyclohexane-dimethanol, ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or mixtures of at least two of these diols are preferred, especially mixtures of 1,4- butanediol, 1,5-pentanediol, and 1,6-hexanediol. Furthermore, polyester polyols of lactones, e.g., ecaprolactone or hydroxycarboxylic acids, e.g., aromatic or preferably aliphatic polycarbonxylic acids and/or derivatives thereof and multivalent alcohols in the absence of catalysts or preferably in the presence of esterification catalysts, preferably in an atmosphere of inert gases, e.g., nitrogen, carbon dioxide, helium, argon, etc., in the melt at temperatures of 1500 to 2500 C, preferably 1800 - 2200 C, optionally under reduced pressure, up to the desired acid value which is preferably less than 10, especially less than 2. In a preferred embodiment, the esterification mixture is subjected to polycondensation at the temperatures mentioned above up to an acid value of 80 to 30, preferably 40 to 30, under normal pressure, and then under a pressure of less than 500 mbar, preferably 50 to 150 mbar. The reaction can be carried out as a batch process or continuously. When present, excess glycol can be distilled from the reaction mixture during and/or after the reaction, such as in the preparation of low free glycol-containing polyester polyols usable in the present invention. Examples of suitable esterification catalysts include iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation may also be performed in liquid phase in he presence of diluents and/or chlorobenzene for aziotropic distillation of the water of condensation.

To produce the polyester polyols, the organic polycarboxylic acids and/or derivatives thereof and multivalent alcohols are preferably polycondensed in a mole ratio of 1:1 - 1:8, more preferably 1:1.05 - 1.2.

After transesterification or esterification, the reaction product can be reacted with an alkylene oxide to form a polyester polyol mixture. This reaction desirably is catalyzed. The temperature of this process should be from about 800 C to about 1700 C, and the pressure should generally range from about 1 to 40 atmospheres.

While the aromatic polyester polyols can be prepared from substantially pure reactant materials, more complex ingredients can be used, such as the side stream, waste or scrap residues from the manufacture of phthalic acid, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, and the like. Compositions containing phthalic acid residues for use in the invention are (a) ester-containing byproducts from the manufacture of dimethyl terephthalate, (b) scrap polyalkylene terephthalates, (c) phthalic anhydride, (d) residues from the manufacture of phthalic acid or phthalic anhydride, (e) therephthalic acid, (f) residues from the manufacture of terephthalic acid, (g) isophthalic acid, (h) trimellitic anhydride, and (i) combinations thereof. These compositions may be converted by reaction with the polyols of the invention to polyester polyols through conventional transesterification or esterification procedures.

Other materials containing phthalic acid residues are polyalkylene terephthalates, especially polyethylene terephthalate (PET), residues or scraps. Still other residues are DMT process residues, which are waste or scrap residues from the manufacture of dimethyl terephthalate (DMT).

Polyoxyalkylene polyether polyols, which can be obtained by known methods, are preferred for use as the polyhydroxyl compounds. For example, polyether polyols can be produced by anionic polymerization with alkali hydroxides such as sodium hydroxide or potassium hydroxide or alkali alcoholates, such as sodium methylate, sodium ethylate, or potassium ethylate or potassium isopropylate as catalysts and with the addition of at least one initiator molecule containing 2 to 8, preferably 3 to 8, reactive hydrogens or by cationic polymerization with Lewis acids such as antimony pentachloride, boron trifluoride etherate, etc., or bleaching earth as catalysts from one or more alkylene oxides with 2 to 4 carbons in the alkylene radical. Any suitable alkylene oxide may be used such as 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, amylene oxides, styrene oxide, and preferably ethylene oxide and 1,2-propylene oxide and mixtures of these oxides. The polyalkylene polyether polyols may be prepared from other starting materials such as tetrahydrofuran and alkylene oxide-tetrahydrofuran mixtures; epihalohydrins such as epichlorohydrin; as well as aralkylene oxides such as styrene oxide. The polyalkylene polyether polyols may have either primary or secondary hydroxyl groups.

Included among the polyether polyols are polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, block copolymers, for example, combinations of polyoxypropylene and polyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethylene glycols, poly-1,4-tetramethylene and polyoxyethylene glycols, and copolymer glycols prepared from blends or sequential addition of two or more alkylene oxides. The polyalkylene polyether polyols may be prepared by any known process such as, for example, the process disclosed by Wurtz in 1859 and Encyclopedia of Chemical Technology, Vol. 7, pp. 257 - 262, published by Interscience Publishers, Inc. (1951) or in U.S. Pat.

No. 1,922,459.

Polyethers which are preferred include the alkylene oxide addition products of polyhydric alcohols such as ethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1, 2-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, hydroquinone, resorcinol glycerol, glycerine, 1,1,1- trimethylolpropane, l,l,l-trimethylolethane, pentaerythritol, 1,2,6-hexane- triol, a-methyl glucoside, sucrose, and sorbitol. Also included within the term "polyhydric alcohol" are compounds derived from phenol such as 2,2-bis(4 hydroxyphenyl)-propane, commonly known as Bisphenol A.

Suitable organic amine initiators which may be condensed with alkylene oxides include aromatic amines such as aniline, N-alkylphenylene-diamines, 2,4'-, 2,2'-, and 4,4'-methylenedianiline, 2,6- or 2,4-toluenediamine, vicinal toluenediamines, o-chloro-aniline, paminoaniline, 1,5-diaminonaphthalene, methylene dianiline, the various condensation products of aniline and formaldehyde, and the isomeric diaminotoluenes; and aliphatic amines such as mono, di-, and trialkanolamines, ethylene diamine, propylene diamine, diethylenetriamine, methylamine, ethanolamine, diethanolamine, N-methyl and N-ethylethanolamine, N-methyl- and N-ethyldiethanolamine, triethanolamine, triisopropanolamine, 1,3-diaminopropane, 1,3-diaminobutane, and 1,4-diaminobutane.

Preferable amines include mono- and diethanolamine, vicinal toluenediamines, ethylenediamines, and propylenediamine. in a particularly preferred embodiment, at least one of the polyether polyols employed is initiated with an initiator containing or consisting of an aliphatic amine, and more preferably, all of the polyols used are initiated with an initiator containing an amine, most preferably an aliphatic amine. It is to be understood that the polyols initiated by an amine can also be initiated with a polyhydric alcohol, such as when a mixed initiator of an aliphatic amine/polyhydric alcohol is used like an amine/sucrose package.

Suitable polyhydric polythioethers which may be condensed with alkylene oxides include the condensation product of thiodiglycol or the reaction product of a dicarboxylic acid such as is disclosed above for the preparation of the hydroxyl-containing polyesters with any other suitable thioether glycol.

The hydroxyl-containing polyester may also be a polyester amide such as is obtained by including some amine or amino alcohol in the reactants for the preparation of the polyesters. Thus, polyester amides may be obtained by condensing an amino alcohol such as ethanolamine with the polycarboxylic acids set forth above or they may be made using the same components that make up the hydroxyl-containing polyester with only a portion of the components being a diamine such as ethylene diamine.

Polyhydroxyl-containing phosphorus compounds which may be used include those compounds disclosed in U.S. Pat. No. 3,639,542.

Preferred polyhydroxyl-containing phosphorus compounds are prepared from alkylene oxides and acids of phosphorus having a P205 equivalency of from about 72 percent to about 95 percent.

Suitable polyacetals which may be condensed with alkylene oxides include the reaction product of formaldehyde or other suitable aldehyde with dihydric alcohol or an alkylene oxide such as those disclosed above.

Suitable aliphatic thiols which may be condensed with alkylene oxides include alkanethiols containing at least two -SH groups such as 1, 2-ethanedithiol, 1,2-propanedithiol, 1,2-propanedithiol, and 1,6-hexanedithiol; alkene thiols such as 2-butene-1,4-dithiol; and alkyne thiols such as 3-hexyne-1,6-dithiol.

Also useful in association with the polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol are polymer modified polyols, in particular, the so-called graft polyols. Graft polyols are well known to the art and are prepared by the in situ polymerization of one or more vinyl monomers, preferably acrylonitrile and styrene, in the presence of a polyether or polyester polyol, particularly polyols containing a minor amount of natural or induced unsaturation. Methods of preparing such graft polyols may be found in columns 1 - 5 and in the Examples of U.S. Pat.

No. 3,652,639; in columns 1 - 6 and the Examples of U.S. Pat. No.

3,823,201; particularly in columns 2 - 8 and the Examples of U.S.

Pat. No. 4,690,956; and in U.S. Pat. No. 4,524,157; all of which patents are herein incorporated by reference.

Non-graft polymer modified polyols such as those prepared by the reaction of a polyisocyanate with an alkanolamine in the presence of a polyol as taught by U.S. Pat. Nos. 4,293,470; 4,296,213; and 4,374,209; dispersions of polyisocyanurates containing pendant urea groups as taught by U.S. Pat. No. 4,386,167; and polyisocyanurate dispersions also containing biuret linkages as taught by U.S. Pat. No. 4,359,541 are also useful.

As a blowing agent, water is employed. The amount of water will at least in part depend upon the desired foam density. For the foams of the present invention, suitable free rise densities are greater than 1.7 pcf to less than about 3.5 pcf, preferably 2.0 pcf to 2.5 pcf. To satisfy these density limitations, the amount of water utilized in TDI foam formulations is typically in the range of 2.5 to about 4.4 pbw, preferably from 3.2 pbw to 4.2 pbw, more preferably from 3.5 pbw to 3.9 pbw, based on 100 pbw of the isocyanate reactive component. Water is useful as a blowing agent in that it reacts with the organic isocyanate to produce urea linkages and liberate carbon dioxide gas. However, it has been discovered that the amount of water employed must be carefully controlled since higher water levels generate more urea linkages and thus result in harder foams generally.

Catalysts may be employed which greatly accelerate the reaction of the compounds containing hydroxyl groups and with modified or unmodified polyisocyanates. Examples of suitable compounds are cure catalysts which also function to shorten tack time, promote green strength, and prevent foam shrinkage. Suitable cure catalysts are organometallic catalysts, preferably organorin catalysts, although it is possible to employ metals such as lead, titanium, copper, mercury, cobalt, nickel, iron, vanadium, antimony, and manganese. Suitable organometallic catalysts, exempli fied here by tin as the metal, are represented by the formula: R,Sn[X-R1 -Y]2, wherein R is a C1 - Cg alkyl or aryl group, R1 is a C0 - C18 methylene group optionally substituted or branched with a C1-C4 alkyl group, Y is hydrogen or an hydroxyl group, preferably hydrogen, X is methylene, an -S-, an -SR2COO-, -SOOC-, an -O3S-, or an -OOC- group wherein R2 is a C1-C4 alkyl, n is 0 or 2, provided that R1 is Co only when X is a methylene group. Specific examples are tin (II) acetate, tin (II) octanoate, tin (II) ethylhexanoate and tin (II) laurate; and dialkyl (1 - 8C) tin (IV) salts of organic carboxylic acids having 1 - 32 carbon atoms, preferably 1 - 2- carbon atoms, e.g., diethyltin diacetate, dibutyltin diacetate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltinmaleate, dihexyltin diacetate, and dioctyltin diacetate. Other suitable organotin catalysts are organotin aloxides and mono or polyalkyl (1 - 8C) tin (IV) salts of inorganic compounds such as butyltin trichloride, dimethyl- and diethyl - and dibutyl- and diocryl- and diphenyl- tin oxide, dibutyltin dibutoxide, di(2-ethylhexyl) tin oxide. Preferred, however, are tin catalysts with tin-sulfur bonds which are resistant to hydrolysis, such as dialkyl (1 - 20C) tin dimercaptides, including dimethyl-, dibutyl-, and dioctyl- tin dimercaptides.

Tertiary amines also promote urethane linkage formation, and include triethylamine, 3-methoxypropyl-dimethylamine, triethylenediamine, tributylamine, dimethylcyclohexylamine, dimethylbenzylamine, N-methyl-, N-ethyl- and N-cyclohexylmorpholine, N,N,N',N'tetramethylethylenediamine, N, N, N' ,N'-tetramethylbutanediamine or -hexanediamine, N,N,N'-trimethyl isopropyl propylenediamine, pentamethyldiethylenetriamine, zetramethyldiaminoethylether, bis(-dimethylaminopropyl)urea, dimethylpiperazine, l-methyl-4-dimethylaminoethylpiperazine, 1,2-dimethylimidazole, l-azabicylo[3.3.0] octane and preferably 1,4-diazabicylot2.2.2] octane, and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldierhanolamine and dimethylethanolamine.

In a preferred embodiment, a delayed action tertiary amine gel catalyst is employed to promote improved froth flow characteristics. Any of the above tertiary amines can be employed. Examples of suitable organic acid blocked amine gel catalysts are the acid blocked amines of triethylenediamine, Nethyl or methyl morpholine, N,N dimethylamine, N-ethyl or methyl morpholine, N,N dimethylaminoethyl morpholine, N-butylmorpholine, N,N' dimethylpiperazine, bis(dimethylamino-alkyl)-piperazines, 1,2 dimethyl imidazole, dimethyl cyclohexylamine. The blocking agent can be an organic carboxylic acid having 1 to 20 carbon atoms, preferably 1 - 2 carbon atoms. Examples of blocking agents include 2-ethyl-hexanoic acid and formic acid. Any stoichiometric ratio can be employed with one acid equivalent blocking one amine group equivalent being preferred. The tertiary amine salt of the organic carboxylic acid can be formed in situ, or it can be added to the polyol composition ingredients as a salt.

The polyol composition optionally contains a flame retardant.

Examples of suitable phosphate flameproofing agents are tricresyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloropropyl) phosphate, and tris(2,3-dibromopropyl) phosphate. In addition to these halogen substituted phosphates, it is also possible to use inorganic or organic flameproofing agents, such as red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate (Exolit) and calcium sulfate, molybdenum trioxide, ammonium molybdate, ammonium phosphate, pentabromodiphenyloxide, 2,3-dibromopropanol, hexabromocyclododecane, dibromoethyldibromocyclohexane, expandable graphite or cyanuric acid derivatives, e.g., melamine, or mixtures of two or more flameproofing agents, e.g., ammonium polyphosphates and melamine, and, if desired, corn starch, or ammonium polyphosphate, melamine, and expandable graphite and/or, if desired, aromatic polyesters, in order to flameproof the polyisocyanate polyaddition products. In general, from 2 to 40 weight percent, preferably from 5 to 20 weight percent, of said flameproof ing agents may be used based on the weight of the isocyanate reactive composition.

Examples of suitable surfactants are compounds which serve to support homogenization of the starting materials and may also regulate the cell structure of the plastics. Specific examples are salts of sulfonic acids, e.g., alkali metal salts or ammonium salts of fatty acids such as oleic or stearic acid, of didecylbenzene or dinaphthylmethanedisulfonic acid, and ricinoleic acid, foam stabilizers, such as siloxaneoxyalkylene copolymers and other organopolysiloxanes, oxyethylated alkyl-phenols, oxyethylated fatty alcohols, paraffin oils, castor oil esters, ricinoleic acid esters, Turkey red oil and groundnut oil, and cell regulators, such as paraffins, fatty alcohols, and dimethylpolysiloxanes. The surfactants are usually used in amounts of 0.01 to 5 wt. %, based on the weight of the polyol composition.

The organic polyisocyanates employed include 2,2'-diphenylmethane diisocyanate and the corresponding isomeric mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates and polyphenylenepolymethylene polyisocyanates (polymeric MDI). In addition, other organic polyisocyanates including aliphatic, cycloaliphatic, araliphatic and preferably aromatic multivalent isocyanates may be employed in limited amounts. Specific examples of optional polyisocyanates include: alkylene diisocyanates with 4 to 12 carbons in the alkylene radical such as 1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1,4-tetramethylene diisocyanate and preferably 1,6-hexamethylene diisocyanate; cycloaliphatic diisocyanates such as 1,3- and 1,4- cyclohexane diisocyanate as well as any mixtures of these isomers, l-isocyanato-3,3,5-trimethyl-5-isocyanatome- thylcyclohexane (isophorone diisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate as well as the corresponding isomeric mixtures, 4,4'-2,2'-, and 2,4'-dicyclohexylmethane diisocyanate as well as the corresponding isomeric mixtures and preferably aromatic diisocyanates and polyisocyanates such as 2,4- and 2,6-toluene diisocyanate. The organic di- and polyisocyanates can be used individually or in the form of mixtures. However, the organic polyisocyanate component will include at least about 15.0 weight percent MDI and/or polymeric MDI.

Frequently, so-called modified multivalent isocyanates, i.e., products obtained by the partial chemical reaction of organic diisocyanates and/or polyisocyanates may also be employed to a limited extent. Examples include diisocyanates and/or polyisocyanates containing ester groups, urea groups, biuret groups, allophanate groups, carbodiimide groups, isocyanurate groups, and/or urethane groups. Specific examples include organic, preferably aromatic, polyisocyanates containing urethane groups and having an NCO content of 33.6 to 15 weight percent, preferably 31 to 21 weight percent, based on the total weight, e.g., with low molecular weight diols, triols, dialkylene glycols, trialkylene glycols, or polyoxyalkylene glycols with a molecular weight of up to 1500; modified 4,4'-diphenylmethane diisocyanate or 2,4- and 2,6-toluene diisocyanate, where examples of di- and polyoxyalkylene glycols that may be used individually or as mixtures include diethylene glycol, dipropylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, and polyoxypropylene polyoxyethylene glycols or -triols. Prepolymers containing NCO groups with an NCO content of 25 to 9 weight percent, preferably 21 to 14 weight percent, based on the total weight and produced from the polyester polyols and/ or preferably polyether polyols described below; 4,4'-diphenylmethane diisocyanate, mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, 2,4- and/or 2,6-toluene diisocyanates or polymeric MDI are also suitable. Furthermore, lipid polyisocyanates containing carbodiimide groups having an NCO content of 33.6 to 15 weight percent, preferably 31 to 21 weight percent, based on the total weight, have also proven suitable, e.g., based on 4,4'- and 2,4'- and/or 2,2'-diphenylmethane diisocyanate and/or 2,4'- and 4,4'-diphenylmethane diisocyanate, polymeric MDI, 2,4'- and/or 2, 6-toluene diisocyanate.

Crude polyisocyanates may also be used to a relatively limited extent in the compositions of the present invention, such as crude toluene diisocyanate obtained by the phosgenation of a mixture of toluenediamines or crude diphenylmethane isocyanate obtained by the phosgenation of crude diphenylmethane diamine.

The preferred or crude isocyanates are disclosed in U.S. Pat. No.

3,215,652.

The following examples illustrate the nature of the invention and should not be considered as limitations thereto. Unless otherwise indicated, all parts are expressed in parts by weight.

Polyol A is a propylene oxide, ethylene oxide, glycerine adduct containing 21 weight percent ethylene oxide, having a theoretical functionality of 3.0, and a hydroxyl number of 27.5.

Polyol B is a propylene oxide, ethylene oxide, trimethylol propane adduct containing 78 weight percent ethylene oxide, having a theoretical functionality of 3.0 and a hydroxyl number of 24.0.

Polyol C is a propylene oxide, ethylene oxide, glycerine adduct containing 73 weight percent ethylene oxide, having a theoretical functionality of 3.0 and a hydroxyl number of 46.0.

B4113 is a silicone surfactant available from Goldschmidt.

Polycat 77 is an amine cataly

TABLE I

Sample A B | C Polyol A 96.05 -- - Polyol B -- 96.05 - Polyol C - - - 96.05 water 2.85 2.85 2.85 B4113 .25 .25 .25 Polycat 77 .60 .60 .60 SA 610 50 .25 j .25 .25 To prepare the samples set forth in Table II, the required weights of the resins listed in Table I were added separately to 23.6 grams of ISO A utilizing standard mix techniques including a German mix blade at 3100 rpm at a quart cup factor of 0.059.

TABLE II

Sample 1 Sample 2 Sample 3 Resin A 50.0 g 40.0 g 40.0 g Resin B - - 10.0 g Resin C - - 10.0 g ISO A 23.6 g 23.6 g 23.6 g The reaction profile for Sample 1 showed a cream time of 14 sec., a top of cup time of 58 sec., a string gel time of 70 sec., and an end rise time of 94 sec. To calculate the density, the net weight of the cup 55.49 g was multiplied by the cup factor 0.059 giving a density of 3.218 pcf.

The reaction profile for Sample 2 showed a cream time of 14 sec., a top cup time of 55 sec., a string gel time of 65 sec., and an end rise time of 104 sec. Surprisingly, the cup net weight fell to 50.9 g thereby giving a calculated density of 50.9 * 0.059 = 3.003 pcf.

The reaction profile of Sample 3 showed a cream time of 14 sec., a top of cup time of 55 sec., a string gel time of 65 sec., and an end rise time of 104 sec. Again, the cup net weight fell unexpectedly to 48.77 g resulting in a calculated density of 48.77 g * 0.059 = 2.88 pcf.

Claims (26)

Claims

1. A low density, flexible polyurethane foam comprising the reaction product of: a) an isocyanate reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500; b) a catalyst; c) a blowing agent consisting of water; d) a crosslinker; e) optionally a surface active agent; and f) an isocyanate composition wherein the resulting foam has an average density of less than about 3.5 pcf.

2. The polyurethane foam of claim 1, wherein said polyol blend has an average hydroxyl equivalent weight of between about 1500 to about 2200.

3. The polyurethane foam of claim 1, wherein said polyol blend has a weight average molecular weight of greater than 4200.

4. The polyurethane foam of claim 1, wherein said polyol blend has a weight average molecular weight of between about 4700 to about 6800.

5. The polyurethane foam of claim 1, wherein said polyol blend has an average hydroxyl number ranging from about 20 to about 60 mgKOH/g.

6. The polyurethane foam of claim 5, wherein said polyol blend has an average hydroxyl number ranging from about 25 to about 45 mgKOH/g.

7. The polyurethane foam of claim 1, wherein said polyol blend includes from about 8.0 wt. % to about 30.0 wt. % of said ethylene oxide/propylene oxide heteric polyol.

8. The polyurethane foam of claim 7, wherein said polyol blend includes from about 10.0 wt. % to about 20.0 wt. % of said ethylene oxide/propylene oxide heteric polyol.

9. The polyurethane foam of claim 1, wherein said polyol blend includes from about 18.0 wt. % to about 24.0 wt. % of said ethylene oxide capped polyol.

10. The polyurethane foam of claim 9, wherein said polyol blend includes from about 20.0 wt. iO to about 22.0 wt. % of said ethylene oxide capped polyol.

11. The polyurethane foam of claim 1, wherein the total amount of said at least one ethylene oxide/propylene oxide heteric polyol and said at least one ethylene oxide capped polyol in said polyol blend is at least ~ wt. % based on the total amount of said polyol blend.

12. A resin composition useful for production of polyurethane foams comprising: a) an isocyanate reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500; b) a catalyst; c) a blowing agent consisting of water; d) a crosslinker; and e) optionally a surface active agent.

13. The resin composition of claim 12, wherein said polyol blend has an average hydroxyl equivalent weight of between about 1500 to about 2200.

14. The resin composition of claim 12, wherein said polyol blend has a number average molecular weight of greater than 4200.

15. The resin composition of claim 12, wherein said polyol blend has a (number or weight) average molecular weight of between about 4700 to about 6800.

16. The resin composition of claim 12, wherein said polyol blend has an average hydroxyl number ranging from about 20 to about 60 mgKOH/g.

17. The resin composition of claim 16, wherein said polyol blend has an average hydroxyl number ranging from about 25 to about 45 mgKOH/g.

18. The resin composition of claim 12, wherein said polyol blend includes from about 8.0 wt. % to about 30.0 wt. % of said ethylene oxide/propylene oxide heteric polyol.

19. The resin composition of claim 18, wherein said polyol blend includes from about 10.0 wt. % to about 20.0 wt.

of said ethylene oxide/propylene oxide heteric polyol.

20. The resin composition of claim 12, wherein said polyol blend includes from about 18.0 wt. % to about 24.0 wt. % of said ethylene oxide capped polyol.

21. The resin composition of claim 20, wherein said polyol blend includes from about 20.0 wt. % to about 22.0 wt. % of said ethylene oxide capped polyol.

22. The polyurethane foam of claim 1, wherein the total amount of said at least one ethylene oxide/propylene oxide heteric polyol and said at least one ethylene oxide capped polyol in said polyol blend is at least 8 wt.

based on the total amount of said polyol blend.

23. A method for producing a low density, flexible polyurethane foam comprising the steps of: reacting a composition comprising: a) an isocyanate reactive component including a polyol blend comprising at least one ethylene oxide/propylene oxide heteric polyol and at least one ethylene oxide capped polyol wherein the polyol blend has an average hydroxyl equivalent weight of at least about 1500; b) a catalyst; c) a blowing agent consisting of water; d) a crosslinker; and e) optionally a surface active agent with f) an isocyanate composition; wherein the resulting foam has an average density of less than about 3.5 pcf.

24. A polyurethane foam as claimed in claim 1 made from a resin composition of any of claims 12 to 19.

25. A polyurethane foam as claimed in claim 1 and substantially as hereinbefore described or exemplified.

26. A method for producing a polyurethane foam as claimed in claim 23 carried out substantially as hereinbefore described or exemplified.